Cloud seeding
Methods of dispersion include aircraft and ground-based generators, with newer approaches involving drones delivering electric charges to stimulate rainfall, or infrared laser pulses aimed at inducing particle formation.
Despite decades of research and application, cloud seeding's effectiveness remains a subject of debate among scientists, with studies offering mixed results on its impact on precipitation enhancement.
Environmental and health impacts are considered minimal due to the low concentrations of substances used, but concerns persist over the potential accumulation of seeding agents in sensitive ecosystems.
The practice has a long history, with initial experiments dating back to the 1940s, and has been used for various purposes, including agricultural benefits, water supply augmentation, and event planning.
Legal frameworks primarily focus on prohibiting the military or hostile use of weather modification techniques, leaving the ownership and regulation of cloud-seeding activities to national discretion.
This strategy of "dynamic" seeding assumes that the additional latent heat adds buoyancy, strengthens updrafts, ensures more low-level convergence, and ultimately causes rapid growth of properly selected clouds.
[citation needed] Since 2021, the United Arab Emirates have been using drones equipped with a payload of electric-charge emission instruments and customized sensors that fly at low altitudes and deliver an electric charge to air molecules.
[9] Despite decades of research and application, cloud seeding's effectiveness remains a subject of debate among scientists, with studies offering mixed results on its impact on precipitation enhancement, according to a report issued by the US Government Accountability Office in December 2024.
Based on its findings, Stanford University ecologist Jerry Bradley said: "I think you can squeeze out a little more snow or rain in some places under some conditions, but that's quite different from a program claiming to reliably increase precipitation."
[13]: 13 A 2010 Tel Aviv University study claimed that the common practice of cloud seeding to improve rainfall, with materials such as silver iodide and frozen carbon dioxide, seems to have little if any impact on the amount of precipitation.
[19] With an NFPA 704 health hazard rating of 2, silver iodide can cause temporary incapacitation or possible residual injury to humans and other mammals with intense or chronic exposure.
These findings likely result from the minute amounts of silver generated by cloud seeding, which are about one percent of industry emissions into the atmosphere in many parts of the world, or individual exposure from tooth fillings.
Environmentalists are concerned about the uptake of elemental silver in a highly sensitive environment affecting the pygmy possum, among other species, as well as recent high-level algal blooms in once pristine glacial lakes.
To his astonishment, as soon as he breathed into the deep freezer, he noted a bluish haze, followed by an eye-popping display of millions of microscopic ice crystals, reflecting the strong light rays from the lamp illuminating a cross-section of the chamber.
Schaefer was able to cause snow to fall near Mount Greylock in western Massachusetts after he dumped six pounds (2.5 kg) of dry ice into the target cloud from a plane after a 60-mile (100 km) easterly chase from the Schenectady County Airport.
[35] Dry ice and silver iodide agents are effective in changing super-cooled clouds' physical chemistry, and thus useful in augmenting winter snowfall over mountains and, under certain conditions, in lightning and hail suppression.
While not a new technique, hygroscopic seeding for enhancement of rainfall in warm clouds is enjoying a revival, based on positive indications from research in South Africa, Mexico, and elsewhere.
From 1967 to 1972, the U.S. military's Operation Popeye cloud-seeded silver iodide to extend the monsoon season over North Vietnam, specifically the Ho Chi Minh Trail.
[37] One private organization that offered, during the 1970s, to conduct weather modification (cloud seeding from the ground using silver iodide flares) was Irving P. Krick and Associates of Palm Springs, California.
The High Plains Cooperative Pilot Project (HIPLEX) focused on convective cloud seeding to increase rainfall during the growing season in Montana, Kansas, and Texas from 1974 to 1979.
Hydro Tasmania also undertook soil and water survey samples and found negligible trace elements of the materials used for cloud seeding (such as silver iodine), and determined it did not have a detrimental effect on the environment.
[52] Pakistan has undergone its first-ever artificial rain experiment using cloud seeding, in a move carried out with the help of the United Arab Emirates.there was drizzle in 'at least 10 areas' of Lahore, consistently ranked the most polluted city in the world.
[53] On Friday, November 15, 2024, Pakistan successfully conducted a cloud seeding operation using locally developed technology, resulting in artificial rainfall to tackle the region’s smog crisis.
[59] Israel stopped the rain enhancement project in 2021 due to the experiment data showing that the practice was largely ineffective and expensive, and because there had been some recent years of unrelated significant rainfall.
On 20 June 2013, Indonesia said it will begin cloud-seeding operations following reports from Singapore and Malaysia that smog caused by forest and bush fires in Sumatra have disrupted daily activities in the neighboring countries.
Results were disappointing; while it did not take long for the rain clouds to form and release precipitation, they often drifted away from Route Provinciale 41 in the process, reducing their ability to hinder Việt Minh logistics.
Ralph Langeman, Lynn Garrison, and Stan McLeod, all ex-members of the RCAF's 403 Squadron, attending the University of Alberta, spent their summers flying hail suppression.
[86] Data collated since the 1960s suggests huge agricultural sector losses are avoided yearly with the protection system, unseeded the hail will flatten entire regions, with seeding this can be reduced to minor leaf damage from the smaller hailstones that failed to melt.
[115] Cloud seeding has been the focus of many theories based on the belief that governments manipulate the weather in order to control various conditions, including global warming, populations, military weapons testing, public health, and flooding.
[116][117] A 2016 classified ad placed by Los Angeles County's Department of Public Works in the Pasadena Star News sparked claims that widespread weather modification was being confirmed.
